1. Technical Field of the Invention
The present invention generally relates to an air cleaner, and more specifically, relates to an air cleaner installed within a ceiling of a clean room used for manufacturing elements or devices such as semiconductor or liquid crystal arrangements.
2. Description of Related Art
A construction of an air cleaner in a related art will be explained referring to FIGS. 13-15. The air cleaner D in the related art has a fan F, a filter 5 and a housing 1 for accommodating the fan F and the filter 5 as shown in FIG. 13. The fan F includes a vane wheel 2, a motor 3 to rotate the vane wheel 2. A motor base 4 supports the motor 3 in the housing 1. The housing 1 has an air inlet 6a at its upper plate 1a, and has an opening at its bottom portion for installing the filter 5. A pressurizing chamber P is formed inside the housing 1 in an upper stream side of the filter 5.
The vanewheel 2 is directly connected to a rotational shaft of the motor 3, and driven rotatively by the motor 3 so as to take in air from the air inlet 6a. When the vanewheel 2 rotates, the air from the air inlet 6a is sucked through a sucking port 2b of the vanewheel 2 and is blown out from a blowing port 2c of the vanewheel 2. The air blown out from the blowing port 2c is supplied to the pressurizing chamber P for increasing a static pressure thereof and is then supplied to the filter 5. The filter 5 purifies the air by removing such small particles having diameters as small as 0.1 micrometers. At the air inlet 6a, a bell mouth 6 is provided on the opposite side of the sucking port 2b in order to smooth a flow of the air which is sucked.
Since this kind of air cleaner is installed within the ceiling, it is designed to have a light weight to make its installation easy. For this reason, the housing 1 is generally formed by thin metal sheet. As one potential problem, sometimes an inspection or a maintenance is performed from an upper side of the air cleaners after they are installed, I.e. via a space provided above the ceiling. In this case, when a worker steps e.g., inadvertently on an upper plate of the air cleaner, the upper plate 1a is likely to be disadvantageously deflected or deformed (i.e., bent) by the weight of the worker. In the related art, the motor base 4 is fixed to the housing in such a manner that the motor base 4 is disposed in parallel to, and independently of, the upper plate 1a. When the worker steps on the upper plate 1a, the upper plate 1a is deflected or deformed inward, while the vane wheel 2 attached on the motor base 4 through the motor 3 stays in a same position. Consequently, the bell mouth 6 on the upper plate 1a and the vane wheel 2 disadvantageously have a gap therebetween narrowed, and in a worst case, the bell mouth 6 and the vanewheel 2 contact each other. Further, narrowing the gap between the bell mouth 6 and the vane wheel 2 increases a pressure loss between the air inlet 6a and the blowing port 2a, 2c, resulting in a deterioration of fan efficiency and an increase of noise level. Further, when the bell mouth 6 and the vanewheel 2 contact each other, mechanical locking of the motor 3 and/or destruction of the vanewheel 2 can occur.
Another problem in the related art is explained with reference to FIGS. 14 and 15. More particularly, as shown in FIGS. 14 and 15, the air 12 blown out of the fan F makes a rotational flow 14 within a horizontal plane which includes the blowing port 2c of the fan F in the pressurizing chamber P, such lengthening an air flow path from the blowing port 2c to the filter 5 and resulting in an increase of a pressure loss. In addition, since each corner of the pressurizing chamber P is formed to have substantially right angle, a vortex flow 13 is formed within such corners by an air turbulence, which deteriorates the efficiency of the blow by increasing static pressure loss.
For example, Japanese Utility Model Application Laid-Open No. HEI 5-63619 discloses an air cleaner of above type. In such related art, air (indicated by an arrow in FIG. 1 thereof) is blown out from the fan 4 and also makes a rotational flow within the horizontal plane including the blowing port 7, 8 of the fan 4 in the pressurizing chamber 6. The rotational flow is forced to flow downward guided by an inner surface of a vertical wall of the pressurizing chamber 6. A guide piece 6' is disposed at a lower portion of the vertical wall so as to guide the air flow along the vertical wall toward a central portion of the panel filter 1. In this related art, the air blown out of the fan 4 also makes a rotational flow within the horizontal plane including the blowing port of the fan 4 in the pressurizing chamber, since the pressurising chamber has a similar construction to that of the related art. This arrangement also has such problems as increasing static pressure loss by a lengthened air flow path and by a formation of a vortex flow.
Further shown in the present FIG. 13 is a related art member 100 which is sometimes provided next to the motor base 4. However, such member 100 is of insufficient thickness/rigidity to provide any support to the motor base 4. Further, such member 100 does not extend between the motor base 4 and upper wall 1a, and therefore does not provide support to the upper wall 1a.